Broadcast and multicast are methods for transmitting datagrams from a single source to several destinations, i.e. point-to-multipoint connection. The 3GPP (3rd Generation Partnership Project) specifications Release-4 and Release-99 define a cell broadcast service (CBS) allowing for low bit-rate data to be transmitted as a message-based service to all subscribers in a set of given cells over a shared broadcast channel. Furthermore, an IP-Multicast service is defined allowing for mobile subscribers to receive multicast traffic. However, this service does not allow for multiple subscribers to share radio or core network resources and as such does not offer any advantages as far as resource utilization is concerned within a PLMN (Public Land Mobile Network) and over a RAN.
In general, a broadcast/multicast service is a unidirectional point-to-multipoint service in which data is efficiently transmitted from a single source to multiple terminal devices or user equipments (UE) in the associated broadcast service area. Cell Broadcast services may be received by all users who have enabled the specific broadcast service locally on their UE and who are in the cell broadcast area defined for the service. In contrast thereto, multimedia broadcast/multicast i.e. MBMS services can only be received by such users that are subscribed to a specific multicast/broadcast service, and in addition in a multicast mode have joined the multicast group associated with the specific service. Multicast/broadcast subscription may be performed either upon user selection or due to home environment initiation.
It is noted that the abbreviation “UE” in this specification refers to both mobile terminal or mobile station (MS) in GSM (Global System for Mobile communications) terms and user equipment in UMTS (Universal Mobile Telecommunications System) terms.
It is envisaged that for some applications, multiple users can receive the same data at the same time. The benefit of multicast and broadcast in the network is that the data is sent once on each link. For example, in case of a GPRS (General Packet Radio Services) based core network, a Serving GPRS Support Node (SGSN) will send data once to a Radio Network Controller (RNC) of the RAN regardless of the number of base station devices, e.g. Node Bs in UMTS terms, and to UEs that wish to receive it. The benefit of multicast and broadcast on the air interface is that many users can receive the same data on a common channel, thus not clogging up the air interface with multiple transmissions of the same data.
With increasing use of high bandwidth applications in 3rd generation mobile systems, especially with a large number of users receiving the same high data rate services, efficient information distribution is essential. Thus, broadcast and multicast are techniques to decrease the amount of data within the network and use resources more efficiently.
Point-to-multipoint services are expected to be used extensively over wireless networks, so that there is need for a capability in the PLMN to efficiently support them. In the 3GPP specifications TS 22.146 and TR 23.846, a Multimedia Broadcast/Multicast Service (MBMS) is defined to provide this capability for broadcast/multicast services offered by the home environment and other value added service providers. The MBMS is a unidirectional point-to-multipoint bearer service in which data is transmitted from a single source entity to multiple recipients. In particular, a broadcast mode and a multicast mode is defined as modes of operation of the MBMS.
An assumption made in the above 3GPP specifications for MBMS defines that for each MBMS service, the respective Control RNC (CRNC) or Serving RNC (SRNC) should have an MBMS context. In practice, this means that service contexts are configured at the RNC, which are not assigned to any specific UE, whereas this context is used by a number of UEs in the cell. In order to link this context with the UE specific active set e.g. of RRC (Radio Resource Control), i.e. the set which describes all the connections (i.e. Radio Access Bearers (RAB) and Radio Bearers (RB)) assigned for the UE in question, it is required that the RNC should detect those UEs which are requesting the MBMS service and for which MBMS services the RNC has already generated corresponding MBMS contexts. The RRC is a sublayer of the radio interface Layer 3 existing in the control plane only, which provides information transfer service to the non-access stratum, e.g. the core network. RRC is responsible for controlling the configuration of radio interface Layers 1 and 2 according to the OSI (Open System Interconnection) protocol layer architecture.
At present all additions and removals of radio access bearers (RAB) or radio bearers (RB) into/out the RRC active set only involve UE-specific transactions and no other relations are needed to check. However, in the present case, when the establishment of an MBMS context and a corresponding RRC connection for a UE occur at different timings, a new linking procedure is required to enhance efficiency and resource utilization.
Furthermore, according to the present MBMS specifications, the RNC cannot check whether a specific UE is authorized to receive the requested MBMS service. This authorization is needed in order to release all faulty requested RRC connections as soon as possible and in this way decrease the possibility of a misuse of RAN resources by UEs.
It is to be noted that the above problems underlying the present invention are not restricted to the above exemplary MBMS service but apply to any network-created service context which triggers generation of at least one terminal connection.